 /*******************************************************************************
  * Copyright (c) 2000, 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.internal.expressions;

 import org.w3c.dom.Element ;

 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IAdapterManager;
 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.Platform;

 import org.eclipse.core.expressions.EvaluationResult;
 import org.eclipse.core.expressions.ExpressionInfo;
 import org.eclipse.core.expressions.IEvaluationContext;

 public class AdaptExpression extends CompositeExpression {

     private static final String ATT_TYPE= "type"; //$NON-NLS-1$

     /**
      * The seed for the hash code for all adapt expressions.
      */
     private static final int HASH_INITIAL= AdaptExpression.class.getName().hashCode();
     
     private String fTypeName;
     
     public AdaptExpression(IConfigurationElement configElement) throws CoreException {
         fTypeName= configElement.getAttribute(ATT_TYPE);
         Expressions.checkAttribute(ATT_TYPE, fTypeName);
     }

     public AdaptExpression(Element element) throws CoreException {
         fTypeName= element.getAttribute(ATT_TYPE);
         Expressions.checkAttribute(ATT_TYPE, fTypeName.length() > 0 ? fTypeName : null);
     }

     public AdaptExpression(String typeName) {
         Assert.isNotNull(typeName);
         fTypeName= typeName;
     }

     public boolean equals(final Object object) {
         if (!(object instanceof AdaptExpression))
             return false;
         
         final AdaptExpression that= (AdaptExpression)object;
         return this.fTypeName.equals(that.fTypeName)
                 && equals(this.fExpressions, that.fExpressions);
     }

     protected int computeHashCode() {
         return HASH_INITIAL * HASH_FACTOR + hashCode(fExpressions)
             * HASH_FACTOR + fTypeName.hashCode();
     }
     
     /* (non-Javadoc)
      * @see Expression#evaluate(IVariablePool)
      */
     public EvaluationResult evaluate(IEvaluationContext context) throws CoreException {
         if (fTypeName == null)
             return EvaluationResult.FALSE;
         Object var= context.getDefaultVariable();
         Object adapted= null;
         IAdapterManager manager= Platform.getAdapterManager();
         if (Expressions.isInstanceOf(var, fTypeName)) {
             adapted= var;
         } else {
             if (!manager.hasAdapter(var, fTypeName))
                 return EvaluationResult.FALSE;
         
             adapted= manager.getAdapter(var, fTypeName);
         }
         // the adapted result is null but hasAdapter returned true check
 // if the adapter is loaded.
 if (adapted == null) {
             if (manager.queryAdapter(var, fTypeName) == IAdapterManager.NOT_LOADED) {
                 return EvaluationResult.NOT_LOADED;
             } else {
                 return EvaluationResult.FALSE;
             }
         }
         return evaluateAnd(new DefaultVariable(context, adapted));
     }
     
     public void collectExpressionInfo(ExpressionInfo info) {
         // Although the default variable is passed to the children of this
 // expression as an instance of the adapted type it is OK to only
 // mark a default variable access.
 info.markDefaultVariableAccessed();
         super.collectExpressionInfo(info);
     }
 }

